I saw a single blue-green light in the sky traveling north to south at a high rate of speed without a sonic boom or engine noise.

I saw a small, blue-green light, similar to what might be on an aircraft, steady and unblinking, traveling from north to south. I was driving westbound on HWY 52 and was nearing the interchange with I-5. It was shortly after 9:30p.m. and I was heading to work. There was some patchy fog along the coast, on the other side of Mt. Soledad. I live near Miramar Marine Corps Air Base, which does have frequent military aircraft and helicopters that fly out to the ocean, and turn southward before flying back to the east. I have grown up as a Navy dependent, and I also served in the Navy for some time, so I am used to seeing aircraft maneuvers and flybys. What struck me was the incredible speed of this object. I did not see any shape of the aircraft itself, only the light, which looked like a beacon. I did not hear any jet noise either. The object, or light, did not appear to be circling south and then east, as I would expect having seen other aircraft use this flight path. Instead, it continued southward, and I lost it as it passed behind Mt. Soledad, which would make the object appear to be somewhere over the ocean, and even further away. Unfortunately, I can not give a fair approximation of the distance it covered, due to it being dark, and initially when I saw the light, I didn't have a point of reference to place it near, but due to the incredible speed that the object moved in the 3 seconds that I saw it, I believe that this was not normal, whenever I have seen an jet fly this fast, I have expected to hear a sonic boom with it. There was none. I have tried to reconcile that an illusion brought on by the fog, may be part of this, but it still does not make sense. I was hesitant in reporting this to you, but thought perhaps it might help, if anyone else reports a sighting from the same area at the same time and date.